1. Field of the Invention
Embodiments of the invention generally relate to processing systems for large substrates.
2. Background of the Related Art
Thin film transistors (TFT) are commonly used for active matrix displays such as computer and television monitors, cell phone displays, personal digital assistants (PDAs), and an increasing number of other devices. Generally, flat panels comprise two glass plates having a layer of liquid crystal materials sandwiched therebetween. At least one of the glass plates includes one conductive film disposed thereon that is coupled to a power source. Power, supplied to the conductive film from the power source, changes the orientation of the crystal material, creating a pattern display.
With the marketplace's acceptance of flat panel technology, the demand for larger displays, increased production and lower manufacturing costs have driven equipment manufacturers to develop new systems that accommodate larger size glass substrates for flat panel display fabricators. Current glass processing equipment is generally configured to accommodate substrates up to about one square meter. Processing equipment configured to accommodate substrate sizes up to and exceeding 1½ square meters is envisioned in the immediate future. Such large substrates represent a substantial investment to flat panel display fabricators. In order to monitor and correct defects during processing, flat panel display fabricators are increasingly turning toward device testing during the fabrication stage. One such device which enables flat panel display fabricators to test devices formed on flat panels is a PUMA™ electron beam tester available from AKT, Inc., a division of Applied Materials, Inc., located in Santa Clara, Calif.
An electron beam tester provides process testing of the thin film transistor matrix. The electron beam test offers several test methods. It can be used for sensing pixel voltages in response to the voltage applied across the pixels or the pixel may be driven by the beam by providing a current to charge up the pixel. The pixel response to the current may be monitored to provide defect information.
During testing, each pixel must be positioned under the electron beam. This is accomplished by positioning the flat panel on an X/Y table positioned below the beam. As the X/Y table moves laterally to sequentially position each pixel below the electron beam, an area must be dedicated around the X/Y table to provide space for this movement.
However, as testing equipment is increased in size to accommodate larger flat panels, simple scaling of current equipment designs would result in disadvantageously large equipment footprints. Correspondingly, larger equipment footprint per processing unit throughput results in a high cost of ownership to the equipment owner. Moreover, the large size of the equipment also increases the cost of shipping and may, in some cases, restrict the means and locales to which such equipment may be transported.
Therefore, there is a need for a compact testing system for flat panel displays.